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O-Benzyl chitosan formed cholesteric liquid crystalline phase in concentrated solutions．The helicoidal behavior (including mainly helix pitch and twist sense) of this polymer was studied by means of circular dichroism (CD)．The higher the concentration was

the larger the pitch was

implying the twisting power decreased with the increase of concentration．Two kinds of absorption can be observed in CD spectra．A broad and strong band appeared at 570 nm

but another sharp and weak band appeared at 330 nm．The former arose from the supermolecular helicoidal structure of cholesteric layers；the latter may arise from the helical conformation of chains．Both levels of helicoidal structures changed their signs

when the concentration or solvent varied．When the solution concentration increased (using dioxane as solvent)

the two levels of helicoidal structures inversed from left-handed to right-handed one by one．When chloroform was used as solvent and the concentration was 65wt％

the handedness of the two helicoidal structures was left-handed (positive Cotton effect)

hut when dioxane or THF was used with the same concentration

a reversed handedness was observed．The influence of solvent may be related to the formation of hydrogen bonds between the solvent molecules and the polymer chains．